MAN-MADE MINERAL FIBRES
i. ehemical and Physical Data
'Man-made minerai fibres' is a generic term that denotes fibrous inorganic substances
made primarily from rock, clay, slag or glass. These fibres can be classified into three general
groups: glass fibres (comprising glasswool and glass filament), rockwool and slagwool, and
ceramic fibres.
'Mineral wool' is a term that has been used to describe rockwool, slagwool and, in sorne
publications, also glasswool. ln this monograph, the terms 'rockwool', 'slagwool' and
'glasswool' are used rather than 'mineraI wool', whenever possible.
The term 'wool' is used synonymously with fibre when describing vitreous or glassy
material that has been attenuated without the use of a nozzle. Fibres that are dra wn through
nozzles are referred to as filaments or continuous fibres (Loewenstein, 1983; W orld Health
Organization, 1983).
Synonyms and trade namesl:
Glasswool: lM (Johns Manvile) 100; lM 102; lM 104; lM 110
Glass filament: ES 3; ES 5; ES 7
Rockwool: G + H
Slagwool: RH; ZI
Ceramic fibre: Fiberfrax; Fibermax; Fireline Ceramic; Fybex; MAN; Nextel; PKT;
Saffil
1.1 Glass fibres
Glass fibre is produced either as glasswool or glass filament. Glasswool is produced by
drawing, centrifuging or blowing molten glass and comprises cylindrical fibres of relatively
short length (compared to fiaments) (Boyd & Thompson, 1980; McCrone, 1980). Glass
rials
includes longer, large-diameter filaments for textile and reinforcing applications as well as
fine-diameter filaments (Mohr & Rowe, 1978).
filaments are continuously drawn or extruded from molten glass. This class of mate
lOnly those synonyms and trade names used in this monograph are listed.
-39-
IARC MONOGRAPHS VOLUME 43
40
ln the production of glass fibres, finely-powdered sand is used as the major source of
silica, and kaolin clay and synthetic aluminium oxides are the most common sources of
aluminium. Boric oxide is introduced primarily from colemanite (a natural calcium borate),
boric acid and boric acid anhydride. Powdered dolomite (CaMg(CO)hl or burnt dolomite
(MgO.CaO) is used to introduce magnesium oxide (magnesia) and calcium oxide. Uncalcined and calcined limestone are used as magnesia-free sources of calcium oxide. Fluorspar
(CaF2) is used to introduce fluoride. Sodium sulphate is added to the glass mixture as a
firing agent and to assist in dissolving residual grains of sand. Iron oxide (Fe20)) may be
added to assist the fibre-drawing process (Loewenstein, 1983; Harben & Bates, 1984).
Compositions of some types of glass used in fibre manufacture are shown in Table 1.
Table 1. Composition (% by weight) of glassesa used in fibre manufactureb
Component
Si02
A1203
CaO
MgO
B203
Na20
K20
Zr02
Li20
F2C
Fe203
GE, electrical fibre component; C, chemical glass (used in, e.g., surfacing mats for corrosion resistance);
A, common soda lime type; S, high-strength, high-modulus (for high-performance structures); AR, alkali
resistant (for reinforcement of concrete)
bFrom Loewenstein (1983)
cFluorine present in glass presumably as fluorides
'E' glass was first developed for electrical applications, but currently over 99% of aH
continuous filament produced is of this type. 'E' glass is generally not defined by compo-
sition, but rather by its electrical properties, which are related to its low alkali oxide content
(less than 1 % sodium, potassium or lithium oxide) (Loewenstein, 1983). 'E' glass is insoluble
in hydroch10ric acid (Miler, 1975).
'c' glass is characteristic of the glass types used to produce glasswool. It is chemicaHy
resistant and is also used in composites that come into contact with mineraI acids and as a
rial in bituminous roofing sheet (Loewenstein, 1983).
'A' glass, produced from inexpensive glass scrap, is a soda-lime-silica glass. It currently
represents an insignificant proportion of world fibre production (Loewenstein, 1983) and is
reinforcement mate
used only in glass fibre insulation (Watts, 1980).
MAN-MADE MINERAL FIBRES
41
'S' glass is a high-strength glass developed in about 1960 for applications such as rocket
motor cases. Produced only in the USA, it is difficult and costly to make and is therefore
limited to very sophisticated, high-technology use (Loewenstein, 1983).
'Cemfil' and 'AR' glass are used for cement reinforcement. These fibres, designed to
impart strength and support, can reinforce 20-30 times their weight of cement (Loewenstein,
1983). 'Cemfil' and 'AR' glass differ in composition from other glasses by the inclusion of
zirconium oxide, which provides the alkali-resistant property necessary for cement reinforcement but also renders the glass more difficult to process (Lee, 1983).
Table 2 presents the composition of some typical commercial glass fibres based on
another classification of glass types (low alkali, lIme-alumina borosilicate (1); soda-lime
borosilicate (II, III); soda-lime (IV); lime-free borosilicate (V); and high lead silicate (VI)).
Table 2. Composition (% by weight) of sorne typical commercial glass
fibresa
Component
SiOi
AliO)
CaO
MgO
Bi03
NaiO
KiO
ZrOi
TiOi
PbO
Fb
Glass type
V Vi
II
II
iv
65.0
4.0
22.0
14.0
3.0
5.5
8.0
0.5
73.0
2.0
5.5
3.5
8.5
0.5
59.0
4.5
16.0
5.5
3.5
11.0
0.5
59.5 34.0
14.5
16.0
14.5 0.5
54.5
5.0 3.0
7.0
3.5
4.0
8.0
59.0
2.0
aFrom National InstItute for Occupational Safety and Health (1977a)
bFluorine present in glass presumably as fluorides
Type IV is used very frequently in glass fibres. Table 3 presents some of the characteristics
and physical properties of fibrous glass made from these six glass types (National Institute
for Occupational Safety and Health, 1977a).
Glass filaments are primarily made from 'E' glass with the following typical composition
(% by mass): SiOi, 53.5-55.5; CaO, 21.0-24.0; A1i03, 14.0; Bi03, 5.0-8.0; alkaline oxides,
0.5- 1.5; CaFi, 0.0-0.8; MgO, 0-2; minor oxides, ~1 .0. Glass filaments exhibit the
following properties: high tensile strength, dimensional stability, high heat resistance,
resistance to chemical attack, high thermal conductivity, low moisture absorption, high
dielectric strength and flame resistance. One type of glass filament has a softening point of
849°C and a specifie gravit
y of 2.63 g/ cm3 (PPG Industries, 1984).
IARC MONOGRAPHS VOLUME 43
42
Table 3. Characteristics and physical properties of sorne commercial
fibrous glassa
Glass
type
1
II
Form
Fibre diameter
range (t.im)
(gj cm3)
Refractive
index
Textiles, mats
6-9.5
2.596
1.548
Mats
Textiles
10-15
II
Wool (coarse)
6-9.5
7.5-15
IV
Packs (coarse)
115-250
V
W 001, fine
0.75-5
0.25-0.75
6-9.5
ultrafine
Vi
Textiles
Specifie gravit
y
2.540
1.541
2.605
1.49
2.465
1.512
2.568
1.537
4.3
GFrom National Institute for Occupational Safety and Health (1977a)
The fibre size of bulk fibrous glass is characterized by the nominal diameter (the median
distribution of length-weighted diameters in random bulk samples of the product). Table 4
rials by their nominal diameter
shows a system that is used to designate glass fibre mate
ranges. Tables 5 gives the nominal fibre diameters and the types of binders used for a
number of commercial products. The most common resins are phenol-formaldehyde and
melamine-formaldehyde (Dement, 1975). More recent data suggest that somewhat lower
nominal fibre sizes are associated with building insulation; 3.75-7.5 lLm for low-density
products and up to 15 lLm for roof boards (Owens-Corning Fiberglas Corp., 1987).
Table 4. US glass fibre size designations and assocIated diarnetersa
Fibre size
designation
Nominal diameter (t.im)
Min
Max
Fibre size
designation
AAAAA
AAAA
AAA
AA
0.05
0.20
0.50
0.75
0.20
0.50
0.75
J
1.50
A
1.50
2.52
M
N
P
B
2.52
3.81
C
3.81
D
5.08
6.35
7.62
8.89
10.12
5.08
6.35
7.62
8.89
10.12
E
F
G
H
aFrom Corn (1979)
11.43
K
L
Q
R
S
T
U
Nominal diameter (¡.m)
Min
Max
11.43
12.70
13.97
15.24
16.51
17.78
19.05
12.70
13.97
15.24
16.51
17.78
19.05
20.32
21.58
22.86
24.13
20.32
21.58
22.86
24.13
25.40
MAN-MADE MINERAL FIBRES
43
Table 5. Nominal fibre diameters and binders for commercial fibrous glass
productsa
Product
Nominal fibre
Type of binder
diameter (lLm)
Waal praducts
General thermal insulation
Moulded pipe insulation
6-15
Lightweight aircraft insulation
7-9
i. 0-1.
High-temperature insulation and filter paper
0.05-3.0
Textile praducts
Continuous filament electrical insulation
'Silver' type electrical insulation
Plastic reinforcing mat
Wrap-on pipe insulation
6-9.5
7-9.5
6-9.5
3.5
Resin
Resin
Resin
Resin
Coatings
Lubricant
Resin
Resin
aFrom Dement (1975)
Individual fibres in a given product have a range of diameters. The range is generally
sman for continuous filaments and much wider for woo1-type fibres.
1.2 Rockwool and slagwool
Rockwool and slagwool are produced by blowing, centrifuging or drawing molten rock
or slag.
Rockwool is typicany made from igneous rocks such as diabase, basaIt and olivine, and
carbonate rocks containing 40-60% calcium and magnesium carbonates (Mansmann et al.,
1976; Fowler, 1980; World Health Organization, 1983). Rockwool remains in the glassy
state because it is cooled so rapidly that it does not recrystallize. It dissolves in dilute
hydrochloric acid (Miler, 1975).
Slagwool is made from the fused agglomerate by-products of certain metal smelting
processes (Mansmann et aL., 1976; Fowler, 1980; World Health Organization, 1983) and its
composition is thus a reflection of the range of components in the different slags used in the
melt (Stettler et aL., 1982). The properties ofthe fibre vary not only according to the sources
ch. One typical composition (%) is: SiOi, 41;
Ali03, 11; CaO, 35; MgO, 6; Fei03, 5; miscellaneous, 2 (sorne sulphur is present). Slagwool
made from Alabama furnace slags had the fonowing composition (%): SiOi, 33-36; Ali03,
of raw mate
rial but also from batch to bat
11 - 14; CaO, 35-42; MgO, 6-13; Fei03, 0-23; S, trace-1.66. The absence of significant
amounts of sodium and boron is typical of slagwool; it is essentially a calcium aluminium
silicate with varying amounts of magnesium and iron, and is usuany slightly soluble in
hydrochloric acid (Miler, 1975).
The composition of sorne European and US rockwoo1 and slagwool insulation materials
is given in Table 6 (Mansmann et al., 1976; Owens-Corning Fiberglas Corp., 1987). The
nominal diameters of rockwool and slagwool products are typically 3-8 ¡.m (Cherrie et aL.,
1986).
44
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IARC MONOGRAPHS VOLUME 43
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MAN-MADE MINERAL FIBRES
45
i.3 Ceramic fibres
Ceramic fibres comprise a wide range of amorphous or crystallne, synthetic minerai
fibres characterized by their refractory properties (i.e., stability at high temperatures).
Ceramic fibres are typicany made of alumina, silica and other metal oxides or, less
commonly, ofnonoxide materials, such as silicon carbide(Arledter & Knowles, 1964). Most
ceramic fibres are composed of alumina and silica in an approximate 50/50 mixture.
Monoxide ceramics, such as alumina and zirconia, are composed of at least 80% of one
oxide, by definition; usually, they contain 90% or more of the base oxide, and specialty
products may contain virtually 100%. Other ceramic fibres prepared for special applications
may incorporate thoria, magnesia, berylia, titania, hafnia, yUria or potassium titanate.
N onoxide specialty ceramic fibres, such as silicon carbide, silicon nitride and boron nitride,
have also been produced (Arledter & Knowles, 1964; Miller, 1982; US Environmental
Protection Agency, 1986; Anon., 1987a).
Alumina-silica ceramic fibre may be manufactured in two types: ceramic refractory fibre
and ceramic textile fibre. The main distinction between the two fibre types is their size.
Ceramic textile fibres are typically longer, ranging from about 155 to 250 mm in length, and
have diameters that range from Il to 20 lLm. Refractory fibres are smaner and shorter than
textile fibres, with average diameters of 2.2-5.0 lLm and lengths varying from 40 to 250 mm.
Over 90% of ceramic fibres produced in the USA are refractory fibres (US Environmental
Protection Agency, 1986).
Table 7 presents typical composition and Table 8 chemical and physical properties of
sorne commercial ceramic fibres (Zircar Products, 1 978a,b; Sohio Carborundum Co., 1986;
Fireline, undated; 3M Center, undated; Zircar Products, undated).
a
Table 7. Typical composition of sorne commercial ceramic fibres
Compo-
Alumina
bulk
Fiberfrax(8 Fiberfrax(8
long staple
nt (% by bulk
weight)
-Fibermax(8
bulk
AliO)
49.2
44.0
72.0
43.4
95.0
SiOi
ZrOi
FeiO)
50.5
51.0
27.0
53.9
5.0
ne
TiOi
KiO
NaiO
CaO
MgO
Yi03
BiO)
Fiberfrax(8
HSA
Zirconia Fireline
ceramic
bulk
(Saffil~)
~~.3~
95 and 97.25
62.0
24.0
92.0
5.0
0.06
0.02
0.8
0.97 and 0.53
0.02
0.001
1.6
1.27 and 0.70
0.03
0.20
Nextel(8
312 fibre
0.1
0.10
0.1
0.15 and 0.08
0.05
0.07 and 0.04
0.05
Trace
8.0
0.06 and 0.03
14.0
46
IARC MONOGRAPHS VOLUME 43
Table 7 (contd)
Compo-
Fiberfrax~ Fiberfrax~
nent (%
bulk long staple
Fibermax~
bulk
Fiberfrax~ Alumina Zirconia Fireline
HSA
bulk
bulk ceramic
312 fibre
(Saffl~)
by weight)
Leachable -cio
Nextel~
-cio
Il
-cIO
chlorides
(ppm
(mg/ kg))
Organics
2.47 and 1.36
aFrom Zircar Products (I978a,b); Sohio Carborundum Co. (1986); Fireline (undated); 3M Center (undated); Zircar Products
( undated)
Table 8. Chemical and physical properties of sorne typical ceramic fibresa
Fibre trade name
Fiberfrax~ bulkb
Fiberfrax~ long
Description
Meltingpoint
gravit
("C)
(g/ cm3)
(mean; ¡.m)
y
Fibre
diameter
Fibre length
Fibre surface
(mean; mm) area (m2/ g)
White
White
1790
2.73
2-3
Up to 102
0.5
1790
2.62
5 and 13
Up to 254
NA
White, mullite
1870
3
2-3.5
NA
7.65
1790
2.7
1.2
3
2.5
2040
0.096
3
3
NA
2600
0.24-0.64
3-6
1.5
1700
NA
NA
NA
NA
1700
"?2.7
8-12
NA
Continuous -Cl
stapiè
Fibermax~ bulkb
Specifie
polycrystallne
Fiberfrax~ HSAb
Alumina bulk
(Saffil~)c
Zirconia bulkd
Fireline ceramice
Nextel~ 312 fibn!
(filament)
White to lightgrey
White
White
White to cream
White, smooth,
transparent,
continuous
polycrystallne
metal oxide
aFrom Zircar Products (l978a,b); Sohio Carborundum Co. (1986); Fireline (undated); 3M Center (undated); Zircar Products (undated)
bResistantto attack from most corrosive agents, except hydrofluoric acid, phosphoric acid and strong alkalies; resistant to oxidation and
reduction; high temperature stability, low thermal conductivity, low heat storage, thermal shock resistance, light weight, excellent sound
absorption
cCorrosion resistant; light weight, low thermal conductivity, low thermal mass, thermal shock resistance, high dimensional stability, high
temperature resilience, refractoriness
dResistant to oxidation and reduction; low thermal conductivity, great refractoriness
eHighly resistant to attack from most corrosive agents, except hydrofluoric acid, phosphoric acid and certain strong alkalies; low thermal
conductivity, light weight, thermal shock resistance, moisture resistance
f Corrosion resistant, except for phosphates, al
kali metal salts, colloidal silica, colloidal alumina and castable refractory cements and mortars;
compatible with silicone, epoxy, and phenolic and polyimide matrix materials; high temperature stabiIty, dimensional stabiIty, low specifie
heat, thermal shock resistance, low thermal conductivity, high electrical resistance, moisture resistance, abrasion resistance
NA, not available